Androgen receptor (AR) plays a central role in the growth of normal prostate, and in the two major prostate diseases, benign prostatic hypertrophy (BPH) and prostate cancer (PCa). Hormonal therapy in PCa is directed at ablating testicular androgen production or blocking AR with antagonists (androgen deprivation therapy), which suppresses PCa growth in most patients. Unfortunately, this therapy has substantial negative systemic consequences, and patients eventually relapse with a more aggressive tumor that has been termed androgen independent PCa. Therefore, there has been great interest in the development of more potent AR antagonists and selective androgen receptor modulators (SARMs), which may inhibit AR action in prostate and PCa without blocking AR in tissues outside the prostate (such as muscle and bone). Screening efforts for such drugs have relied on functional assays for effects on a variety of cells, but the molecular basis for these specific effects is not clear. An alternative approach to identify candidate SARMs is to focus on molecular interactions between AR and AR associated proteins that mediate its functions. We have shown that AR can interact with co-repressor proteins, including NCoR and SMRT, and that this interaction is enhanced by mifepristone (RU486), demonstrating that drug induced conformational changes in the AR can enhance co-repressor recruitment. Significantly, the molecular mechanism of action for the selective estrogen receptor modulators (SERMs) appears to be that they favor recruitment of NCoR and SMRT. These observations indicate that it should be possible to identify further drugs that enhance the AR interaction with NCoR and SMRT, and that such drugs will likely have tissue specific effects on AR activity. Based on these considerations, our primary objective is to develop a high throughput molecular screen (HTS) for compounds that enhance AR binding to NCoR and SMRT. Importantly, we have developed a cell based mammalian 2-hybrid protein interaction assay using transiently transfected cells to measure this interaction, and have used it to screen approximately 50,000 compounds. We propose here to develop stably transfected reporter cell lines that will improve upon the transient transfectants and allow for further HTS. If successful, the compounds we identify will provide critical probes to assess tissue specific effects of NCoR/SMRT recruitment, and may serve as lead compounds for prevention or treatment of BPH and PCa.